In a factory where many die-cast machines are used to mold aluminum (including aluminum alloy, same as above), an aluminum material is frequently supplied not only from the inside of the factory but also from the outside of the factory. So far, the material has generally been supplied in the form of an ingot. Recently, transporting a container that accommodates molten aluminum from a factory of a material supplier side to a molding factory side and thereby to supply a material in a molten state to the respective die-cast machines has gradually become common.
A conventional container has a structure like a teapot in which a pourer for use in supply is attached on a sidewall of a container body where molten metal is stored. The molten metal is supplied from the pourer to a storing furnace on a molding side when such a container is inclined.
However, the conventional container is inclined by use of, for instance, a forklift. Such an operation cannot necessarily be safe. Furthermore, in order to largely incline (inclination and rotation operation) the container, the forklift has to be provided with a rotation mechanism. Accordingly, a structure of the forklift necessarily becomes a special. Still furthermore, there is a problem in that a skilled operator is necessary to carry out the inclination operation of the container.
In this connection, a system in which pressure is applied to the inside of a container to supply the molten metal to a storing furnace is proposed. When such a container utilizing a pressure difference is adopted, not only the safety and operability is improved but also more complicated supply service becomes available (JP-UM-A-03-31063 (FIG. 1)).
In the conventional container, the molten metal is introduced into inside of the container by opening a lid provided at an upper portion thereof and dropping the molten metal therefrom. To the contrary, the present inventors have proposed a system in which the inside of a hermetically sealed container is depressurized and a molten metal is externally introduced into the container. For instance, a molten metal is introduced from outside through a molten metal supplying pipe. When such a process is adopted, it is necessary to assuredly detect that the container became full at the time of introduction of the molten metal.
Furthermore, in the container having the abovementioned configuration, there is a problem in that a pipe for supplying a pressurized gas is likely to be clogged. In particular, according to the above-described system, a container is mounted on a truck and transported from one factory to another through a public road. Accordingly, in many cases, the container is wobbled. For this reason, as a liquid level of the molten metal in the container is wobbled, the molten metal is spattered in the container, and thereby adhere to the pipe for supplying pressurized gas. When, for instance, such an adhesion is repeated, the clogging of the pipe occurs.
Still furthermore, in the case that a container of this kind is being transported, the hole connecting the container to a pressurized gas supply port is necessary to be sealed in order that the molten metal would not leak therefrom. In the case of the hole being closed to hermetically seal the container, in some cases, the pressure inside the container is raised owing to the thermal expansion of a gas and so on. As a result, in some cases, a problem arises in that the molten metal is unexpectedly discharged from the pipe for discharging the molten metal. When the lining of the container is insufficiently dried, owing to vaporization of water, a pressure increase in the container becomes remarkable.